


He Blinded Me With Science

by thebananahasspoken



Category: Undertale (Video Game)
Genre: F/M, Female Reader, Gaster/Reader - Freeform, Glasses!Gaster, Groping, Kissing, Lab coats, Professor!Gaster, it's science time buckos, more hands than necessary, non-void Gaster, science talk, sex in public (ish), so no goop
Language: English
Status: Completed
Published: 2016-09-15
Updated: 2016-09-15
Packaged: 2018-08-15 03:15:21
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 8,428
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8040331
Author URL: https://archiveofourown.org/users/thebananahasspoken/pseuds/thebananahasspoken
Summary: “I, uh… I’m sorry, Doctor. I didn’t mean to lose focus. I’ll… get this cleaned up and get back to work,” you excused, ashamed at being caught spacing out and at being so obviously excited by him being close to you, but stopped when Gaster waved a hand through the air, the other sliding up his side to insert itself into his lab coat pocket.“That won’t be necessary. We’ve gotten a lot done today… I think we’ve both earned a break,” he assured you, taking a step towards you; he deliberately lowered his gaze, dragging his sockets over you from head to toe slowly and obviously, so you could clearly see his inspection.“And I believe I know how I would like to spend mine.”





	He Blinded Me With Science

**Author's Note:**

> Whoop whoop, random one-shot time! I have a couple of these up my sleeves, though most have to do more with Sans and Papyrus (from various AUs), and I'll do them every once in awhile as the mood strikes. What we have here is a Gaster x Reader fic, one of the few that I'll ever do lol. Warnings are for explicit sexual material. Nothing super kinky this time, guys <3 but still, no one under 18 please.
> 
> My Tumblr, for updates, fan art, summaries, skele sins, and other shenanigans!  
> http://thebananafrappe.tumblr.com/

* * *

It was too early.

So early it was practically still yesterday, in fact; you were lucky the janitor had been having his breakfast outside the science building so he could let you into it.

The sun hadn’t even thought of rising yet, the horizon the flat blackish purple of a restful night.

Normally you would have still been at home in bed, bundled in as many blankets as you could manage.

It was a Thursday, after all, and Thursday was your sleeping in, doing nothing day; you didn’t have any classes, you had somehow finagled it so that you didn’t have to work…

There was no reason for you to be quick-stepping down the long, dark, tiled hallway running between the chemistry lab and the astronomy lecture hall at four twenty-two in the effing morning on a _Thursday_.

No reason besides the only lit laboratory in the hall, that is, its door ajar and shining a bright triangle of yellow, incandescent light across the floor tiles and up the wall across from it.

Flushing and pulling self-consciously at the hem of your skirt, you slowed your pace and composed your breath, absentmindedly licking your lips and adjusting the braid hanging over your shoulder, before reaching out and pulling the door open, peeking inside the cavernous space within.

The private lab was illuminated by a long panel of light strips set in equal spacing along the ceiling, one in the corner flashing occasionally (one of the bulbs must need changing), showcasing a cluster of long tables, upright chalkboards covered in equations, and lab stations spread out across the floor.

Most of the tables were overflowing with drifts of papers and discarded, half full beakers of multi-colored solutions, dismantled circuitry boards and haphazardly jumbled gears, almost completely obscuring the laminated tabletops.

The lab stations were equally as cluttered, each displaying a different project composed of different areas of science, ranging from anatomy to microbiology to physics.

And standing among the cluttered work surfaces, shuffling through a sheaf of papers composedly, stood the reason that you were here instead of sleeping, his lab coat sleeves rolled up over his bony forearms and his magically lit eye sockets flicking quickly over the unfurled systems chart from behind his reading glasses.

Doctor Gaster had been an enigma from the moment the monsters had risen from the Underground, shocking the world and throwing it into turmoil and entirely predictable chaos; things had settled over the years since then, the monsters proving themselves trustworthy, reliable, non-violent, and possessing of useful skills, and the world had turned.

The doctor himself had buried himself in the sciences of the Aboveground the moment the University had accepted him into their ranks, and ran the whole science department now, proving himself to be proficient in not only physical science, but life and magical science as well, bringing about a new age of discovery and learning to the world.

He was renowned for his work on sustainable energy, bio-prosthetics, and space age material production, his intelligence on par with the greatest minds the human world had ever produced… but his multiple PhDs weren’t the reason you had practically run through the mostly empty and abandoned commons this morning, not the reason you smiled shyly and tapped the edge of one of your heels against the other.

He was a brilliant monster, that went without question…

But he was also, in your eyes, an undeniably handsome and charming one, his intelligence only adding to your flustered fervor when it came to how you looked at him.

He had been your Physics 111 professor in your freshman year at the university, still an oddity in the world; you had never been taught by a monster, though you had gone to and graduated from high school with a few (you had become close friends with a green plasma elemental, in fact), so you had been unsure when stepping through the door into the lecture hall that first day, nervous over the new experience and still new to college itself.

You had been proven to have nothing to worry about, however.

Doctor Gaster was a proficient teacher, instructing alongside his son, a much shorter, easygoing, and comedic skeleton monster named Sans, and though he occasionally slipped into another language entirely when excited over a topic (he had explained that it was called Wing Dings, a form of verbal and written shorthand that he had learned hundreds of years ago and never quite unlearned), he had impressed you, and you had learned a lot in his class.

Unfortunately, though (or was it fortunate? You’d never quite figured it out…), you had also fallen for him.

You had resisted the pull of attraction as best you could, refusing to believe your flushing cheeks and clamoring heart and love-stricken mind, but had been forced to give in when the magnetism persisted for years, only growing stronger every time you saw him or stopped to have a conversation with him.

He became an irresistible force to you, a celestial body that you couldn’t help but be dragged towards, and after you were sure it wasn’t some silly, schoolgirl crush, you didn’t resist.

He drew you in more every time you were close to him.

The way he spoke, his voice deep and melodic and full of invested knowledge....

The way he carried himself, sweeping almost majestically among desks and down hallways, his long tailed, dark coats or stark white lab attire billowing behind his long strides…

The way his long, thin hands would caress the flasks in the lab or gesture through the air…

You had it bad, almost obsessed in your affection, but had been unsure of how to approach him for the longest time.

That is, until he had put out a call for a lab assistant.

His son had been drafted to another college about six months ago, called to be the head of his own department there, leaving Gaster with no dedicated or knowledgeable assistance with his experiments.

He had tried to handle everything himself for a while, juggling classes and his research alone, but, frustrated by how little he got done on his own, had quickly decided he needed help.

You had been more than happy to oblige.

He kept odd hours, case in point this early morning sojourn (he had called twenty minutes ago, waking you from a deep slumber and requesting your help excitedly), but the past months had been some of the best of your life.

You had learned a lot while assisting him, part of some of the most interesting and influential discoveries in the university’s history, but you also got multiple chances to flirt with the brilliant monster while alone in the lab with him at all hours of the night…

And he had not been unreceptive.

It had taken a very long time for him to get that you were coming on to him when you started making moves on him, when you would drag your fingers down his arm or would bend just a little too low when picking something up off the ground, your progressively shorter skirts baring your thighs to him.

He would stare blankly, the most inarticulate you had ever seen him, when you teased him, whatever he had been doing forgotten in his distraction; you chalked it up to him not having people flirt with him very often (you liked that, to be honest… more for you), as he spent a lot of time either alone or with his friends from Underground.

He would ogle you for a few moments after your flirtations, hands limp and sockets blank, but would then return to his tasks, with a flush of purple magic spread across his cheekbones.

He lapsed into Wing Dings more often when he was like that, and some part of you quite enjoyed flustering him so much he couldn’t think straight.

About two months ago, though, he had begun to respond, returning touches and sending you scorching, heated looks; he seemed to enjoy flustering you back, wickedness glinting in his gaze when he got you to blush with a sideways comment or a glimpse of his tongue (you had nearly had a heart palpitation the first time he had summoned it to lick the edge of his coffee cup, and he had noticed).

Nothing had come of it yet, however, the closest thing to intimacy you had managed to wrest from him a comment he had muttered close to your ear three days ago, his hands hovering tantalizingly over your hips as he leaned over your shoulder, the bunsen burner you were using flickering brightly (“You’re playing with fire, little girl… lab safety procedures require me to warn you that you may get burned if you aren’t careful...”).

Which was why you were so excited to be slipping through the door and into the lab at this ungodly hour, hanging up your coat on the rack beside the door and taking down your lab gear.

You had asked for some advice from a monster acquaintance of yours, the owner of a bakery and tea shop a block off of campus; Muffet was a genius baker, and had a booming chain of shops spread across the states.

What she excelled most in, however, was style, always dressed to the nines.

She had recommended, for the seducing of monsters, long stockings (“Not striped, though, dear, just plain colors”) paired with a flirty skirt; you had gone out and bought some fancy black thigh highs just for that reason, and though you felt a little self-conscious about the height of the skirt, or rather the lack of, you hoped this would do the trick.

Smirking hopefully to yourself, you slipped into your lab coat and strutted over to Gaster, his gaze still riveted to the printout in his hands.

“Good morning, Doctor,” you called out, reaching out to pick up a stray clipboard from one of the tables, and, starting slightly (he must have been so engrossed in his reading that he didn’t notice you entering), Gaster looked up at you from over the rim of his glasses, a welcoming smile pulling at the edge of his mouth.

“Good morning indeed; I am glad you are here. The agars have finally set, and are ready for inspection. Come,” he informed you excitedly, the gleam of discovery in his eye (he was so sexy when he was fired up about his work…), and immediately turned on his heel, his long legs carrying him between the leaning piles of papers and stacks of lab equipment effortlessly and gracefully.

Surprised that he hadn’t even noticed your attire, you frowned, stymied in your wavering confidence (you really shouldn’t be all that surprised, honestly… he was the most oblivious genius you’d ever met), but followed after the doctor regardless, acknowledging the need to do your work.

He had been working on a bioengineered skin graft for burn victims, composed of a form of recently discovered, self-regenerating bacteria combined with silicone, and the results looked promising; the new graft system would reduce the recovery time of victims, as well as lower scar tissue formation and chronic pain.

Smiling to yourself ruefully, shaking your head and pulling again at the hem of your skirt, you turned into the doorway that Gaster had disappeared through, letting yourself into the much smaller, warmer room and watching as the doctor pulled a tray of Petri dishes from the incubator, setting them beside a row of microscopes.

He bent at the waist to inspect the round dishes with a critical eye, measuring the growths in them carefully and jotting some notes on a scrap piece of paper, then beckoned to you, indicating that you should come closer and join him.

“You see how the bacteria is consuming the silicone? It will digest it and add the material to its own makeup. The progression is going very well. Today we will be making up some slides to present to the Surgeon General,” he supplied, pointing out several growing cultures on the tray, then glanced at you from the corner of his right eye socket, furor clear in his gaze.

“I will need your assistance for several hours. Can you stay that long?” he queried, hope lifting his tone into fervent animation, and you smiled back at him, your heart thudding in your chest and your cheeks flushing.

What you wouldn’t give for him to talk about you like that...

“Of course I can, doctor. Let’s get to work,” you told him just as passionately, glad to help in anything that made him this happy, and strode over to one of the stools in front of one of the microscopes, hopping up on it and pulling a container of glass slides closer to you.

The two of you worked in comfortable silence for close to two hours, occasionally commenting to each other on one of the slides or comparing notes (and stopping for coffee around the time the sun started rising, a quiet conversation on the wonder of the universe exchanging between you).

You couldn’t claim you were completely focused the entire time, though, getting considerably less done than he did; it was very warm in the room, kept at a certain heat and humidity to encourage the growth of the bacteria, and the warmth made your attention waver occasionally.

Your eyes would dart over to your partner, watching his precise, graceful hands placing slices of culture on slides and then pushing them under the microscope to inspect; you had thought of those hands against your bare skin more than once, flashes of your flesh visible through the holes in the center of them.

And then you would look away and back to your work, even hotter and more spacey than you were before.

These distractions had left you in quite a state, sweat trickling down your back and your panties feeling more than their fair share of wet; you vacillated for several minutes about whether or not you should excuse yourself to get cleaned up, but finally decided that taking your lab coat off should help at least keep you from staining your blouse (your underwear were irredeemable by now).

Settled, you shrugged out of your coat and laid it across the stool on the side opposite to Gaster, having to reach a little to toss the material across its surface, and then turned back to return to your work, crossing your ankles and settling in for another unexciting but fulfilling few hours of slide preparation.

Today wasn’t going how you planned, but you still enjoyed Gaster’s company, and you felt good for being able to help him.

However, as you turned back around, you caught, from the corner of your eye, a glimpse of Gaster hurriedly turning back to his own microscope, a deep violet flush overcoming his cheekbones and, for the first time you remembered, a bead of lilac tinted sweat dripping down the dome of his cracked skull and his glasses hanging precariously from his nasal ridge.

You stared at him from the cover of your bangs, one eyebrow rising suspiciously, then glanced down at yourself, sudden realization dawning over you; he must have seen you moving to take off your coat and glanced over at you, only to finally see your carefully assembled outfit… and the stockings stretched up the lengths of your thighs.

They seemed to be having their intended effect, too…

Smirking deviously, you feigned a yawn, lacing your fingers together and stretching them over your head; you arched your back, letting out a small groan of contentment as you did (and holding back the biggest blush of your life), and then glanced over at the doctor, meeting his diverted and slightly wide-eyed gaze with a blatant wink.

“Mmm… I could use some more coffee,” you murmured hotly, lowering your arms and standing, then swept from the room with as much allure as you could muster, swaying your hips with each step (and feeling slightly ridiculous while doing so; Muffet had said that men liked that, but you felt like you were going to accidentally knock something over).

Once out of his field of vision, you raised both of your hands to your burning cheeks, your eyes wide and fingers shaking at your audacity; this was the boldest that you had been so far, and you were nervous as hell.

Had he even liked that?

Was your outfit even what he had been flushed about?

It _was_ pretty warm in the room, and it was feasible that he had just been overheated like you had been...

You weren’t sure, and not knowing was making you feel a little sick to your stomach; you really liked Gaster, were pretty sure that you were way past like by now, to be honest, but for someone as smart as he was, he could be really dense sometimes.

You wished, and not for the first time, that you could just tell him how you felt instead of playing an almost one sided game with him, but as much as you disliked it when he didn’t respond to your teasing, either not noticing or too focused on other things to get it, when he did understand and responded in kind made the wait more than worthwhile.

Sighing, you lowered your hands away from your face and wandered over the half full coffee pot outside the door to Gaster’s private office, grabbing one of the mugs and the pot to absentmindedly do as you had said you were.

Maybe you should be more direct…

Shrugging, you set your now full cup down on the cluttered desk the doctor was using as a coffee prep station, scooting a book out of the way to make space for it, then fished around in the Styrofoam bowl set on top of the machine, looking for real sugar absentmindedly.

You really should have been paying more attention, though, because, in your dazed and distracted stupor, you don’t notice the tall, lab coat garbed monster slide from the doorway behind you, looking you up and down as he strolled up next to you, his hands folded behind his back and a grin lifting his mouth into sly comeuppance.

He had more than noticed your efforts to catch his eye, the length of your stockings (scandalous...) and the sway of your hips hypnotizing him, and had given chase as soon as he had put the slides and agar back in the incubator.

He had business with you, after all; you had been teasing and coming onto him for the better part of a year now, and had left him in the dark as to why. You were an attractive human, intelligent and driven, and should have had little interest, especially sexual, in an old monster like him.

You hadn’t ceased in your attentions, though, only becoming more blatant, and had responded positively when he began to flirt back… and now today, you had arrived in this garb, seemingly intentionally worn for _him_.

Dinner and proper courting were more his style, but breakfast and sex in his laboratory worked just fine too.

You _had_ volunteered your time to him… he may as well put it to good use.

Smirking and taking note of your preoccupation with your search for sugar, Gaster, lids lowering in knowing seduction, leaned over your shoulder and exhaled against your neck deliberately.

“You seem distracted,” he muttered smoothly, magical irises riveted to your expression from over the rim of his reading glasses, and let out a quiet chuckle when you felt the touch of his breath on your skin and registered his closeness both, the foam bowl and multicolored sugar packets your hand was buried in flying through the air as you jerked in surprise.

Shocked and unfairly stimulated, you stepped back from the amused monster, pouting and rubbing the palm of your hand over your neck, before looking down at the scattered sugar packages around your feet, trying to hide the blush rising up your neck to color your cheeks.

“I, uh… I’m sorry, Doctor. I didn’t mean to lose focus. I’ll… get this cleaned up and get back to work,” you excused, ashamed at being caught spacing out and at being so obviously excited by him being close to you, but stopped when Gaster waved a hand through the air, the other sliding up his side to insert itself into his lab coat pocket.

“That won’t be necessary. We’ve gotten a lot done today… I think we’ve both earned a break,” he assured you, taking a step towards you; he deliberately lowered his gaze, dragging his sockets over you from head to toe slowly and obviously, so you could clearly see his inspection.

“And I believe I know how I would like to spend mine.”

Your heart stuttered in your chest, fulfillment and elation flooding your veins; was he really saying what you thought he was?

You could practically feel the heat of his gaze on your body, could see the intensity and seduction in his hooded sockets, but it seemed too good to be true, too much like wishful thinking, for you to be sure.

You had gotten very little sleep last night… perhaps you had drifted off at your microscope, only dreaming of your affections and desire finally being returned.

Gaster appeared very surprised when you raised one hand and pinched the skin on your upper arm, wincing and hissing at the pain.

“What on earth are you doing?” he asked curiously, stunned and confused by your behavior, and you smiled wanly at him, rubbing your now sore arm and flushing lightly in embarrassment.

“I, uh… was checking if I was dreaming. Silly, I know,” you admitted, lowering your gaze back to the packets of sweetener scattered between where you were both standing, but across from you, Gaster smiled indulgently, walking up to you, uncaring of the sugar he was stepping on, and lifted your chin with one finger.

“Do you dream of me propositioning you often… or only today?” he murmured, rubbing his thumb over your lower lip gently; there was heat in his words and gaze both, and you flushed even more, feeling a little dizzy.

Cripes, he was blowing your mind…

Distracted and floating on a cloud of stupefied bliss, you nervously licked over your lower lip, completely forgetting that his thumb was there, and got your first taste of the monster standing over you; he tasted strongly of the latex of the gloves that he had worn while working, but the smoothness of the bones of his phalanges, so different from skin, made you shudder, and not in a bad way.

And you weren’t the only one.

Gaster twitched at the appearance of your tongue, staring unabashedly when the tip of it flicked over his finger; his gaze sharpened, something that looked like hunger flashing in his sockets, and, enraptured, he took another step closer to you, his other hand slipping from his lab coat pocket to trace the along the length of your neck, sending shivers and gooseflesh all the way down your body.

You spent a moment lost in the feeling of his hands, eyelids dropping and breath panting from between your still spread lips (you had slept with people before, and even with a monster once, but you had been fantasizing about _this_ , about **_him_** , for so long that just the bare touch of his fingers to your skin was driving you crazy), before remembering that he had asked you a question.

You struggled to clear the fog from your hazy, still flabbergasted brain so you could answer, your breath haltering as the tips of his fingers brushed against your pulse, which was beating so fast you were sure he could feel it.

“O-often…” you managed to force out, your hands trembling at your sides, itching to reach out to touch him back but afraid that doing so would shatter what was, surely, still your overactive imagination gifting you with this surreal experience.

He was not of the same inclination, and smirked softly at your admission, shuffling even closer to you to press his chest to yours.

He bent to look into your eyes, the large, graceful hand smoothing along your throat lowering to press into the small of your back, drawing you closer into his embrace.

“Hmm… what a coincidence. I think of having you often,” he breathed against your lips, gaze hooded and heavy, before he pressed his mouth to yours, silencing the gasp of revelation that threatened to leave you at his admission.

You had often marveled at the way a skeleton, usually a completely stationary entity formed of solid material, could move in the ways that he did, the bone of his face expressive and malleable despite the state of its matter, but had never been more surprised by its capabilities than when his mouth was moving against yours, swallowing your breaths and the small noises of appreciation and excitement that you made.

You didn’t know what you had expected, when you had dreamed of doing just this exact thing… but it hadn’t been this, his bony lips prying yours apart to allow the tip of his tongue, soft and sinuous and slick with ectoplasmic saliva, to brush against yours.

You didn’t even notice Gaster was walking you backwards until your back bumped into one of the lab stations, too caught up in arching up to meet his kisses, tangling your tongues together lingeringly; you barely even noticed _that_ beyond feeling the edge of the countertop through your shirt, wondering blankly at how you had ended up next to one of the tables.

You _did_ notice when his hands trailed down your sides to grasp your ass, though.

You pulled from his mouth, panting and gasping as he squeezed the flesh caught in his palms, looking up at him from under lowered, fluttering lashes; your hands flew to his broad shoulders, making contact at last, when he lowered his mouth to your throat, his tongue dragging up the side of your neck slowly, tantalizingly.

“O-oh… _god_ , doctor…” you stuttered out between gasps, your fingers digging into the material of his lab coat and your head dropping back, and against your throat, the tall skeleton monster chuckled, pulling back to grin at you while, at the same moment, pulling you deeper into his embrace with his grip on your posterior, grinding his pelvis against yours.

“Gaster, dear. There is no need for worship or professionalism right now,” he admonished playfully, raising a brow suggestively, and for a moment you could only stare at him, shocked at his display of humor, before guffawing loudly, snorting and covering your face with one hand.

“Pfff… and you say you never joke,” you snickered, tears of hilarity beading at the corners of your eyes (you wiped them on your shoulders distractedly, the heat still beating distractingly through your blood making your head rush), and Gaster, letting out a quiet laugh of his own, shrugged, shaking his head.

“As far as anyone but you knows, I don’t. My son would never let me hear the end of it if he found out,” he lamented, rolling his gaze up to the ceiling in exasperation, and you bit your lip to hold back another giggle, recalling Professor Sans’ penchant for terrible puns (and Gaster’s frustration with them) and drawing your pinched fingers across your mouth in emulation of a zipper.

“My lips are sealed,” you stage whispered, barely hiding your grin, then let out a startled inhalation, the hands still settled on your ass squeezing and reminding you of their presence.

Gaster fixed you with an assured stare, seething with ardor and desire, and pressed you against the table again, drawing your attention back to your previous occupation.

“I certainly hope not…” he rejoined in a seductive mutter, reaching up to remove his glasses, throwing them carelessly onto the table behind you, before bending to trace the tip of his tongue over the parted seam of your lips; his clever wordplay went without comment, as he immediately set to work stealing your breath away again.

Time lost all meaning to you, caught in an ever rising swell of longing and passion; you felt like you were floating, his hands pleasure incarnate and his mouth a sweet escape, redolent of coffee and spearmint and magic.

You made no protest when he used his grip on your posterior to pick you up and sit you on the edge of the lab station behind you, wrapping your legs around his hips and ticking your wandering fingers over the protrusions of his ribs, your hands buried beneath his lab coat.

You _did_ protest when he released your ass to sweep a sheaf of papers onto the floor to better situate you, breaking from his mouth with a heavy blush and a scandalized look at his research scattered over the tiles.

“Doc… Gaster, your work…” you spluttered, trying to scoot off the table to retrieve his documents and store them in a safe place, but were arrested by your partner sliding himself between your thighs, his hands climbing your legs to smooth over the stockings you had donned.

“They are papers, sweet thing. There is nothing on them that cannot be reprinted, or is not already in my head. I know them front and back. You, though… I am only beginning to know,” he assured you, slipping his hands under the hemline of your pleated skirt and pressing his chest to yours, his bony lips a whisper against the hollow of your throat.

“The only work I am concerned with doing right now is you.”

You thought no more of the research spread on the floor after that, especially when he swirled his tongue up the veins of your neck and found the lace of your panties with the tips of his fingers.

His hips took up a gyrating motion against your center, tantalizingly rubbing his pelvis through the wetness that was already seeping through your underwear, and removed one hand from your skirt to slide beneath your blouse, gliding along your sweat dotted skin to grasp your breast.

Gaster let out an odd noise, somewhere between a grunt and a moan, when he found himself unimpeded by a bra, sending you a scorching look from the corner of a socket and pausing in the titillating motion of his tongue momentarily.

“Hopeful, were we?” he teased, flicking his thumb over your beaded nipple, and you flushed accordingly, arching into his touch with both anticipation and pleasure.

“Very. But you already knew that…” you crooned to him, one hand rising to clasp the back of his neck, the protrusions of his cervical vertebrae rasping against your fingers; you leaned further into his hands, dragging your tongue along his jawline.

“What you don’t know about is all the times I didn’t bother with my panties, either,” you whispered against smooth bone, feeling daring and bold, and were answered with a deep, grating hum, something you would have called a growl, from anyone else; his grip tightened marginally, against your hip and your breast, and as he turned his face towards yours, violet magic flared in his sockets, his grin sharp and wicked.

“And what a shame that I didn’t… I’d have had you bent over my desk long before now,” he muttered gutturally, his tongue flicking out to trace over his upper lip line, and suddenly, shockingly, another hand, separate from the two already buried under your clothes, traced a finger up your neck.

Yet another ran its palm down your calf, holding your leg against Gaster’s hips, and a fifth, identical to his own hands in every way but its disembodied nature, pressed its fingertips to your lips, slipping into your mouth to play with your tongue.

“We’ll just have to make up for lost time, won’t we?”

You received no explanation for why he suddenly had five hands, or even _how_ (you assumed it was a part of his magic, something you had never seen him use for anything besides teleportation and lifting objects down from high places not even he could reach), but you didn’t dwell on it, especially when your monster lover’s many fingers were slowly stroking your body into madness.

Smooth, agile phalanges pressed against what seemed like every inch of you, squeezing your breasts and running through your hair and caressing the narrows of your waist.

One pulled your shirt up over your heaving breasts, baring you to Gaster’s sight (a look of rabid hunger overcame his expression, gaze focused entirely on your chest), and another grasped a handful of your hair, pulling back gently to allow him to bite softly at your throat.

You let out a noise you had never heard yourself make before when yet another of his hands slid itself down the front of your panties, delving its fingertips into your sopping folds.

Gaster smirked at your nonverbal exclamation, the fingers now rubbing up and down over your core crooking and sending a shock of stimulation through your whole body, your hands clenching on his shoulders and your back arching.

“ _There_ we are… beautiful. You are gorgeous, pet, hold nothing back…” he encouraged, thrusting one finger into your center, and drank down your cry of ecstasy in a passionate, desirous kiss, consuming what felt like your very soul.

You nearly sobbed in pleasure when he pressed another finger into you, his thumb moving to rub slow circles over your clit; you writhed against him, powerless and panting as he worked your body like an instrument.

It didn’t take him long to bring you to orgasm, with his fingers pumping into you and dragging over your skin and cupping your breasts, shuddering and limp in his capable hands; the descent from your zenith of pleasure was pleasant and smooth, your core clutching at his fingers as he dragged them from you slowly, mindful of your sensitivity.

You didn’t expect him to raise the hand that had been inside you to his mouth, though, or for him to lick your juices from his fingers with a look of rapture, his sockets drifting closed and a hum of contented pleasure escaping him.

Gaster glanced at you, intrigued, when you moaned haltingly while watching him, still hazy from your completion; he grinned connivingly, dragging his tongue over his phalanges one more time before returning his attention back to you.

“Such an enchanting creature you are… delicious and soft and so _responsive_ ,” he muttered, eliciting shivers from you as one of his hands traced its fingers over your still fluttering abdomen.

He leaned over you, pressing a trail of lingering kisses to your cheeks and lips, before taking one of your hands in his, lowering it from his wide shoulders to the front of his pants and clenching your fingers around a hardness that was definitely _not_ bone.

“Let us see if we can further extend your pleasure, shall we?” he whispered against the corner of your mouth, his breath hot and rapid, and in the palm of your hand, the evidence of the monster scientist’s desire twitched, existing despite your mind insisting that it shouldn’t (he was a skeleton, was he supposed to have junk? More magic shenanigans, you assumed, but you weren’t complaining).

You nodded immediately, moving your other hand down to pull the straining zipper on his khakis down while fondling the tented fabric (Gaster was humming below his breath, his many hands smoothing over your skin and erogenous zones encouragingly), and once you’d gotten it down, you wriggled your hand into his pants, the smooth surface of his cock hot against your fingers.

He felt of average thickness as you closed your fingers around him, grinning to yourself at the shudder that ran over his bones at your intimate contact, and a little more than average length, but what surprised you even more than the fact that he had anything in his pants at all (you’d had no expectations there, content at merely having him want you) was the fact that the length of magical dick that you pulled from his slacks was a deep, glowing purple, not unlike the fire still flickering in his sockets.

You stared at it in both amazement and curiosity for a moment, rubbing your thumb over the head (apparently as sensitive as the human counterpart, as it throbbed in your hand, a drop of violet, liquid magic beading at the tip), before attempting to scoot down from the table, wanting to return the favor he had given you.

Two hands locked over your wrists, though, pulling them down to the surface of the lab station, while two others gripped your calves, pulling your legs up to prop around Gaster’s hips; the remaining appendage slid under your chin, lifting your gaze back to meet his intense, voracious one.

“That can wait for another day, precious… I have a different dance in mind,” he implied, bucking his hips forward and rubbing himself against your core through the soaked, twisted crotch of your panties, and you moaned before you could stop yourself, your eyelids drooping and body twitching at the sensation.

“Y-yeah, sure… um, do you need a, um…” you probed, casting your unfocused gaze around the lab to look for your purse and stuttering helplessly (this was really happening… lord above, he actually wanted you…), but Gaster shook his head, one of his hands releasing you to undo his belt.

“Protection is not necessary. A monster cannot impregnate a human except under very special circumstances,” he explained dutifully and reassuringly, popping the button on his pants while his other hands wandered, tracing up your arms and legs lingeringly (the stimulation was incredible), and you nodded a few more times than necessary, excited and nervous.

“Oh, okay… learning new things every day, right? Like that skeleton monsters can do the do,” you joked anxiously, licking your lips and watching, with your heart in your throat, as he grasped his cock in one hand, pumping his fingers up and down its length a few times.

He let out a suave chuckle at your assessment, glancing back to you and smoothing the back of one hand down the side of your face, bending to press a long, heavy kiss to your lips.

“Indeed. Magic can be both a blessing and a curse, though in this case, I believe the former is the most accurate. Are you alright? Are you having reservations?” he asked once he had pulled away from your mouth, staring into your eyes in slight concern, but you shook your head immediately, reaching out to, shakily, trace one of the cracks in his skull.

“No! No, I just… I’ve never been very good, I don’t want to disappoint you…” you began, swallowing against your tension, but, unexpectedly, he let out a disbelieving snort, shaking his head and kissing you again.

“Nonsense. Whoever gave you that impression is a fool, and clearly not aware of how to treat a woman. It takes respect, care, dedication, just the smallest amount of humility… and attention to detail,” he dismissed with something hard in his tone, clearly not impressed with whoever had derided your expertise while, at the same time, dragging one of his hands down to rub at your clit through your underwear, making you cry out in surprised pleasure.

He smiled softly at that, sliding himself further into the cradle of your thighs.

“You see? Give a little to get a little, as they say,” he assured you, then slid the fingers running up and down your sopping center across the material of your panties, dragging them to the side to settle himself against your folds, hot and tingling with magic.

You drew in a ragged breath together, gasping as one at the enticing feeling of closeness, of wetness and raw desire; Gaster dropped to one arm on the counter, the other grasping at your waist while his disembodied hands stroked along your skin, and looked into your eyes again, seeking final confirmation.

You nodded without hesitation, gripping the edge of the counter, and the next moment he was inside you, the thickness of his cock spreading your walls and sending shockwaves through your still sensitive body.

You arched against him immediately, your eyes wide and breath leaving you in a gasp and fingers tightening on the counter; your former orgasm had ensured he had plenty of room to work with, and had sunk himself into your core entirely.

He wasn’t unaffected, his shoulders hunching, his forehead dropping against yours, and his bony lips parting in a groan of ecstasy; he gave a few lazy thrusts in his slump, testing your position and his tolerance, before lifting himself back up to standing fully, hooking his free arm under one of your legs, and setting the palm of the other on the lab station counter.

He grinned down at you, his breath panting from him, before withdrawing himself from you slowly, teasing you with light caresses and the barest of movements; you squirmed beneath him, trying to move your hips to encourage him into going faster, but he declined your open invitation, taking his time in pushing himself in and out of you.

You wanted to demand that he fuck you, that he rut you into the lab station so hard that the rest of his research papers would fall to the ground, usually having no patience for the pace he was using… but you resisted.

There was something beautiful about the way he moved over you, his multiple hands venerating your body and his cock slowly, languidly filling your core; rather than rough and dirty, the way it had been with every other one of your lovers, he was slow and sensual, observant and experienced, and though you ached for another orgasm, for more than the unhurried, steady fervor he was amassing, you couldn’t bring yourself to say anything.

You felt like a goddess, under Gaster’s practiced, dexterous hands, being observed and worshiped in his own temple of intellect and science; you had wanted this, to be the center of his attention, to have him look on you with the interest and fascination that he did with his passion projects, and you were getting it.

There was method to his pace, indistinguishable from mere undulation but present all the same; despite the slowness of his thrusts, despite the gentleness of his hands the and the whispers of praise (“You are so beautiful… you perfect woman… so soft and warm…”), there was heat building in you yet, far more pleasant than the quick explosion and fade of your other experiences, practically luxurious.

He was testing the fullness of both of your limits at his own leisure… and you loved it.

Gaster took his time turning you into a puddle of helpless pleasure, in no rush to end your joining, before giving you the release you sought, rubbing a thumb over your clit and spiraling the already incredible ardor running rampant in your blood higher; your orgasm, when it crested, seemed to go on forever, drawn out by his determined touch and the smooth, sinuous motion of his body against yours.

He coaxed three more from you, each so long and intense that you thought you were going to pass out from sheer pleasure, before he started to lose control.

You were flat on your back by that point, boneless and panting and clutching at the monster slowly driving you mad, sure you would float off into space if you didn’t keep a firm grip on his forearms; you barely noticed him sinking to his elbows over you, his mouth dropping, not for the first time, to lap his tongue over your beaded nipples.

You did notice his hips speeding up against you, though, the urgency in his sudden increase of force quickening your breath and drawing from your hazy indulgence; you lifted your head to look over his face, strained in concentration and dripping with trails of lavender sweat, raising one of your hands to cup his cheekbone.

Gaster looked up at you wearily, small grunts of exertion escaping him as he increased the pressure of his thrusts even more; he grinned crookedly, the most unsteady and disheveled you had ever seen him, and lowered two of his hands to grasp behind your knees, spreading your legs even further for him.

“I think… I believe I have kept you waiting long enough. The table… ah! The table must be hurting your back by now…” he said waveringly, his sockets shuttering in the steady buildup of his own release, his breath hitching and his movements becoming uneven, and you clutched him close to you, summoning the last of your strength to move your hips up into his thrusts, in time with him.

“I can’t feel a thing besides you…” you moaned against the side of his skull, locking your legs around his hips, and it appeared that your encouragement, your moving with him in tandem, was the tipping point; he let out a growl, a real, deep, resonating growl, and gripped the backs thighs tightly in his large hands, pistoning himself into you with desperate need.

“That’s what a monster likes to hear, lover… _stars,_ you are incredible,” he grated huskily, his voice strained and catching on his more and more frequent groans of pleasure; his many hands were pulling you deeper into him with each hard motion of his body, digging into your flesh insistently.

You were starting to lose it too, _again_ (you weren’t sure you were going to be able to walk after this, surely your legs would be useless from coming so much), vocalizing your pleasure so loudly that Gaster, distracted and hapless, flicked one hand over his shoulder at the door into the hallway, slamming it shut with a flare of magic.

Which was a good idea, one that you hadn’t even considered until you heard the lock click, distantly (hopefully no one had walked by…), since you both fell over the edges of your orgasms only a moment later, clinging to each other and crying out fervidly.

Gaster lay over you on the tabletop for a long moment, breathing haggardly against your neck and occasionally twitching (you could feel his cock throbbing inside your core, wetness dripping from around it to puddle on the tile and a few of his research papers); you were in much the same state, incredibly sated.

Slowly, you turned your head to face him, pressing a kiss to his vertebrae; he leaned into the pressure of your lips, groaning beneath his breath, before lifting himself off of you, returning the kiss almost sleepily, and pulling himself from your body, the purple fire fading from his eyes as he did.

While Gaster righted his clothes, tucking his shirt back into his pants, doing up his belt, and retrieving his glasses from the table beside you, you laid limp on the top of the lab station, flushed and happy and feeling like you could sleep for a century.

You could do little more than stare up at the ceiling and marvel, only attempting to pull down your shirt when the air conditioner switched on; you really couldn’t believe you’d had a literal tryst in your associate’s laboratory, laying in the middle of his research notes on… particle physics, it seemed.

It was just too surreal.

Gaster’s hands (the ones attached to his arms; the others seemed to have disappeared as soon as his dick had) setting themselves on your still spread, stocking covered thighs shook you from your considerations of the light panel above you, his satisfied smirk making you more than aware of the cool wetness between your legs.

You were about to ask him if he could fetch you a towel, so you could clean yourself and the area the two of you had dirtied, when he slid his fingers up the inside of your thigh, dragging through his own cum, and pulled your panties back into place, covering you and immediately soaking them.

“There we are… suitable enough. Going forward, though, if you desire to seduce me, I would recommend being more forward than wearing these… admittedly _wonderful_ stockings. I can be quite blind when it comes to things like fashion,” he admitted conversationally, raising his wetted, purple tinted fingers to your mouth (you understood immediately, taking them into your mouth and licking them clean, the taste of his magic tingling against your tongue).

He watched you from under hooded lids for a moment, his smirk growing a bit sharper the longer you licked his phalanges, before pulling his fingers from your mouth and wiping them on his lab coat, then extending his hand to help you up.

“I would like to invite you to breakfast, if you are so inclined. I think we could both use the pick me up. The diner at the corner should be open by now… you enjoy their pancake recipe, if I recall correctly,” he went on, pulling you to your feet on the paper covered floor when you placed your hand into his; there was a wicked glint in his eye despite his civility, which only grew when you smoothed your skirt down, flushing at the feeling of his cum trickling down your thighs.

You looked up at him from under your lashes, heat again building in your lower abdomen at the heaviness of his gaze.

“Of course, I’d love to. Coffee is great to keep you awake, but all I ate before coming here was half a Pop-tart,” you lamented, shifting from foot to foot and trying to ignore your soaked panties, and Gaster, chuckling beneath his breath, placed a hand on your lower back, bending to whisper in your ear.

“One stipulation, dear: while we eat, I’d like you to feel just how naughty you’ve been, tempting me so shamelessly, so no cleaning up until we get back,” he muttered, tracing a finger under your chin coyly, then walked to the hooks behind the closed laboratory door, removing his lab coat and donning his long, black trench coat, leaving you frozen in place, your knees weak and your cheeks bright red.

He turned to look back at you, leering and, teasingly, extending his tongue to lick along his upper lip line.

“If you can behave yourself, and don’t make too much of a mess… I’ll help clean you up myself.”

**Author's Note:**

> Thanks so much for reading, and feel free to leave a comment! If not, I'll seeya around!


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